Answer :
Final answer:
The assassination of Archduke Franz Ferdinand was the spark that ignited World War I.
Explanation:
The event that marked the start of World War I was the assassination of Archduke Franz Ferdinand, heir to the Austro-Hungarian throne, in 1914.
This event led to a chain of events that eventually escalated into a global conflict involving major powers.
The Sinking of the Lusitania, Zimmerman Telegram, and Wilson's Fourteen Points were significant events during the war but not the direct cause of its outbreak.
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Answer: D. Assassination of Archduke of Austria-Hungary
Explanation:
The assassination of Archduke Franz Ferdinand on June 28, 1914, was the main event to start World War 1. The suspect was traced back to a Serbian extremist group that was trying to break up the Austria-Hungary empire and increase Serbian power.